JComboBox

Question

我创建了 JComboBox 并更改了它的背景和前景色。但是我在那里没有看到预期的白灰色垂直线，我不知道如何修复它。这条竖线应该也画了，但是没有。

import javax.swing.*;
import java.awt.*;
import java.util.Arrays;

public class TestComboBox {

    private static final String[] ANIMALS = new String[]{"Cat", "Mouse", "Dog", "Elephant", "Bird", "Goat", "Bear"};
    private static final Color COMBO_COLOR = new Color(71, 81, 93);

    public static class MessageComboBox extends JComboBox<String> {

        public MessageComboBox(DefaultComboBoxModel model) {
            super(model);
            setFont(new Font("Arial", Font.PLAIN, 30));
            setPreferredSize(new Dimension(350, 50));
            setRenderer(new MyRenderer());
        }
    }

    private static class MyRenderer extends DefaultListCellRenderer {

        @Override
        public Component getListCellRendererComponent(JList list, Object value,
                                                      int index, boolean isSelected, boolean cellHasFocus) {

            JComponent comp = (JComponent) super.getListCellRendererComponent(list,
                    value, index, isSelected, cellHasFocus);

            list.setBackground(COMBO_COLOR);
            list.setForeground(Color.WHITE);
            list.setOpaque(false);

            return comp;
        }
    }


    public static void main(String[] args) throws Exception {
        String nimbus = Arrays.asList(UIManager.getInstalledLookAndFeels())
                .stream()
                .filter(i -> i.getName().equals("Nimbus"))
                .findFirst()
                .get()
                .getClassName();

        UIManager.setLookAndFeel(nimbus);
        UIManager.put("ComboBox.forceOpaque", false);

        JFrame jf = new JFrame();
        jf.setSize(800, 400);
        jf.setVisible(true);
        jf.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        jf.setLocationRelativeTo(null);

        MessageComboBox comboBox = new MessageComboBox(new DefaultComboBoxModel(ANIMALS));
        JPanel panel = new JPanel();
        panel.add(comboBox);
        jf.add(panel, BorderLayout.NORTH);
    }
}

也许有人知道如何解决这个问题？

Answer 1

Nimbus defaults say, the default ComboBox.padding is Insets(3,3,3,3) (See Insets doc)。因此，意外的灰线是由于此填充引起的。由于您想删除正确的填充，您可以通过将此行添加到您的第一个 UIManager-call:

来解决您的问题

UIManager.put("ComboBox.padding", new Insets(3, 3, 3, 0));

结果：

JComboBox - 箭头和标签之间的填充/间距

JComboBox - padding / spacing between arrow and label

java

swing

nimbus